The present invention relates generally to benzylated polyalkylene polyamine compounds, curing agent and amine-epoxy compositions derived from such compounds, and articles produced from such compounds and/or compositions.
The uses of epoxy resins which are cured, hardened, and/or crosslinked with amine-based curing agents are well known. These amine-epoxy materials are widely used in applications ranging from coatings, adhesives, and composites, to construction products for concrete, cementitious or ceramic substrates, often referred to as civil engineering applications such as formulations for concrete flooring.
When epoxy resins are cured with neat polyalkylene polyamines such as those based on the ethylenediamine (EDA) homologues, the mixtures will tend to “smoke” or “fume”. This describes the protonation of the amine with water or slight acidity present in the surrounding air. This phenomenon is due to the high amine vapor pressure. Many epoxy coatings based on the EDA homologues suffer from problems referred to in the industry as blush, carbamation, carbonation, or exudate. These problems are all due at least in part to incompatibility of the amine curing agent and epoxy resin, which causes phase separation and results in amine migration to the coating surface. At the surface the amine can react with CO2 present in the air resulting in carbamation, and if water is present a carbonation can occur. Whether in the form of carbamation or the greasy layer known as exudate and blush, this surface defect detracts from the appearance of the coating, and can also lead to problems with intercoat adhesion. (See “Amine-blushing problems? No sweat!”, Fall 2001 Epoxy Formulators' meeting of the Society of the Plastic Industry by Bruce Burton, 17 pp). The problems also tend to be worse when coatings are applied and cured at low temperature, since this exacerbates amine-epoxy incompatibility. In addition, the coating setting time is extended compared to ambient conditions, which leaves a longer time for amine components to migrate to the coating surface. In the case of a clear coat a ripening time may be applied to achieve a coating with high gloss and clarity. Ripening time or incubation time or induction time is defined as the time between mixing epoxy resin with amine and applying the product onto the target substrate. It could also be defined as the time required for the mix to become clear.
There are numerous amine-based curing agent and amine-epoxy compositions that are employed in the amine-epoxy coating industry; however, none of these known products completely addresses the needs or solves the problems noted above. Accordingly, it is to this end that the present invention is directed.